A magnetic random access memory (MRAM) is a non-volatile memory including tunneling magnetoresistive (TMR) elements utilizing tunneling magnetoresistive effect. The MRAM has been drawing attention as a revolutionary next-generation memory which makes it possible to rewrite data without limitation while achieving as high integration density as the dynamic random access memory (DRAM) and as high speed as the static random access memory (SRAM).
The TMR elements are arranged at intersections of word lines and bit lines to be used to read and write signals, for example. The TMR element is used as a memory cell in which an underlayer being the lowermost layer and a cap layer being the uppermost layer are processed to be a lower electrode and an upper electrode, respectively, and are then connected to wiring to play roles as the electrodes.
When an electric current flows vertically from the lower electrode to the upper electrode in the TMR element, the TMR element freely changes the magnetic direction of a magnetization free layer as a ferromagnetic layer, and thereby switches the electric resistance value of the electric current flowing into the an insulating layer between the high and low levels. With the low resistant state and the high resistant state of each TMR element set to “0” and “1,” respectively, the MRAM performs information reading and writing by exchanging the information with the metal wiring.
As a method of manufacturing a magnetoresistive element applicable to the MRAM and the like, Patent Document 1 discloses the invention intended to solve damage caused on a multilayer magnetic film in the processing of the multilayer magnetic film by reactive ion beam etching.
In the invention disclosed in Patent Document 1, a damage layer formed on the multilayer magnetic film in the processing by the reactive ion beam etching is removed with ion beam irradiation. Patent Document 1 discloses that a protection film (made of aluminum nitride or the like) is formed on the clean surface of the magnetic film obtained by removing the damage layer.